I'm just wondering... How would they test that? It would be tough even if the dog could talk.
Scientist: So, Dog, what colour is this.
Dog: Creamy yellow
Scientist: Nope, it's red!
Dog: How do you know that we are not seeing the same colour, but know it by different names?
Scientist: see image

While other animals could possibly see more colors than us (emphasis on could), those colors wouldn't even be colors as colors are specifically the light which is within the visible light spectrum. An animal who could see extra colors would only be looking at ultraviolet/infrared waves

What was saying, is that by literal definition of 'color' humans see all color. "Color" is the light which human eyes can pick up. Any other specific frequency beyond that cannot be comprehended by humans and thus wont have a name- not that it needs one, because we're unable to encounter it

Side note: we can't say the mantis shrimp uses it's advances sight to see past our vis. spectrum, it could orientate its vision to better see our three colors (which would make sense as it would need this to be able to find prey and dispatch it before it got away).

As I just said, it CANNOT see "extra" colors, because color itself is only red, blue and green (and all that's in between). The mantis shrimp is not seeing extra color by human standards, it can only see something outside of our visible range and thus is simply able to perceive ultraviolet and/or infrared. While his would be a color to the shrimp, ultraviolet and infrared are invisible to us and thus are not colors.

Not all of them, what we call the primary colors are only three of the 15 or 16 total colors we can't understand or see. The reason you can't figure out new colors is because your brain can't comprehend it. This goes for everyone.

Humans define color if it is invisible to us it isn't described as color. Organisms who see past the visible light range see ultraviolet/infrared as color but wouldn't be called color because we cannot see past our visual range and humanity made the definition for color